The present invention relates to a cooling system and method for electronic components, and especially a cooling system for electronic components, which is integrated into a LED lamp, especially a retrofit LED lamp. The cooling system according to the present invention works by producing cyclic air pressure fluctuations, which produce cyclic air jets affecting and cooling the surface of the electronic components.
LED lamps, especially retrofit LED lamps, which include one or more light emitting diodes, LEDs, require for operation electronic components. In higher wattage LED bulbs the electronic components produce a significant amount of heat, due to conversion losses. Especially in retrofit LED lamps, which operate with high intensity LEDs, and which are closed by a bulb, the heat generation is extremely high, and can negatively influence the performance and the lifetime of the lamp. Therefore, active or forced cooling of the electronic components inside such a lamp is required. Active or forced cooling is typically achieved by air transport, wherein hot air is transported away from the electronic components or the heat sources in general, and cooler air flows in to replace the hot air. Active cooling by the use of directed air jets, which provide a very turbulent air flow (the so-called Nusselt number the ratio of convective to conductive heat transfer is high), provide a very efficient and concentrated way to remove heat from surfaces of electronic components, in comparison with conventional, fan like solutions.
FIGS. 1a and 1b show a heat sink 10 for a heat source 40, like electronic components of an LED lamp, according to the state of art, which uses a turbulent jet formation for the active cooling. Such state of the art cooling systems typically comprises a chamber 20, which is provided with an engine, which produces an air pressure Pc in the chamber 20, which is lower than the outside air pressure Po in a first “intake” phase, and higher than the outside air pressure Po in a second “jet forming” phase. The chamber 20 has a nozzle 50, through which air is taken in or expulsed from the chamber 20, respectively, depending on whether the air pressure Pc in the chamber 20 is higher or lower than the outside air pressure Po. The nozzle 50 is directed towards one or more heat sink fins 90, onto which a heat source, i.e. an electronic component 40, is attached. The nozzle 50 and the heat sink fins 90 form an air channel, and the nozzle 50 is oriented to the heat fins 90, so that air is taken in or is expulsed, and flows mainly parallel to the orientation of the heat sink fins 90, which have an elongate shape.
In the first phase, the “intake” phase, air is taken in into the chamber 20, and there is no significant cooling effect on the heat sink fins 90. In the second phase, the “jet forming phase”, an air jet is formed in the nozzle 50, indicated by the fat arrow, which is directed along the elongate surface of the heat sink fins 90. The air jet further retains a secondary air flow indicated by the small arrows from the left and the right of the heat sink fins 90, and the highly turbulent flow package washes the surface of the heat sink fins 90, whereby a considerable cooling effect on the fins 90 is achieved.
Apart from the fact that only the “jet forming” phase contributes to the cooling, a further disadvantage of the above state of the art solution is that it is not well suited, for a case, where different electronic components heat up to different temperatures. The state of the art solution needs to interface each electronic component with one of a plurality of different heat sink fins 90, because if only one heat sink fin 90 would be applied to several electronic components 40, the higher heat dissipating electronic components 40 would heat up the other components, which themselves heat up only to a lower temperature. The requirement of multiple heat sink fins 90 in the state of the art solution makes more compact designs impossible. Further, heat sink fins 90 do not provide a direct cooling of the heat source, but an indirect cooling, and heat sink fins 90, which are typically made of metal, provides an additional safety risks, if provided on the outside of the lamp.